Apparatus for making round bales

ABSTRACT

A round baler comprising a baling chamber mounted on a main frame for forming cylindrical packages of crop material therein, the baling chamber being at least partially defined by a pair of side walls and an apron assembly having an inner run which is guided at the inside of a cylindrically shaped continuous wall, and an outer run which is guided at the outside of said continuous wall. The continuous wall is provided with an opening for the recuperation into the chamber of crop material which has been entrained by the apron assembly when the latter left the baling chamber and entered its outer run.

BACKGROUND OF INVENTION

1. Field of Art

This invention relates generally to an apparatus for making cylindricalbales, commonly referred to as a round baler. More particularly, thisinvention pertains to a baler of the type having a fixed bale formingchamber which is at least partially defined by a conveyor which isguided along a continuous cylindrical wall.

2. Description of Art

Prior art balers generally have a bale forming chamber defined by anapron comprising an array of side-by-side belts, transverse slatstrained on chains, a plurality of rolls or a combination of thesevarious elements, e.g. rolls and belts. Crop material such as hay orstraw is picked up from the ground as the baler traverses the field, fedinto a fixed or variable chamber where it is accumulated and compressedto form a cylindrical package of crop material. The formed package,while in its compacted condition inside the chamber, is wrapped withnet, plastic film, twine or the like, to produce a completed round balewhich is then ejected from the chamber onto the ground for subsequenthandling.

A baler having a fixed chamber, that is, a bale forming chamber thatdoes not vary in size, is disclosed in UK Patent Application GB2,001,231 A. The chamber is defined by a pair of floor rolls and acylindrical wall along which the inner run of a conveyor is guided. Thisconveyor comprises a pair of opposing chains between which a pluralityof slats is mounted for engaging and rotating the crop material fed intothe bale forming chamber. The conveyor leaves the chamber at its frontend near the crop inlet and runs upwardly and rearwardly along theoutside of the bale chamber wall to the back of the baler from where itis guided downwardly to enter again into the chamber in the vicinity ofthe floor rolls.

A portion of the crop material fed into the bale chamber may becometrapped between the slats of the conveyor and the cylindrical wall andmay be pulled out of the chamber by these slats. Some material may fallback on the windrow in front of the pick-up unit and be recuperated bythe same, but the rest is carried by the outer run of the conveyor alongthe upper surface of the bale chamber until it reaches the rear portionof the baler from where it falls onto the field and is lost.

SUMMARY OF THE INVENTION

It is an object of the present invention to reduce these losses of cropmaterial and to provide means which, on the one hand reduces the chancethat crop material remains trapped between the slats and the inner wallof the bale chamber, and on the other hand assist in recovering materialwhich has been drawn out of baling chamber by these slats.

According to the invention, there is provided a baler for forming cropmaterial into cylindrical bales, said baler comprising a main frame anda baling chamber mounted on said main frame for forming cylindricalpackages of crop material within.

The baling chamber is partially defined by a pair of side walls and anapron assembly having an inner run which is guided at the inside of acylindrically shaped continuous wall. The apron assembly also has anouter run which is guided at the outside of said continuous wall.

The baler is characterized in that the continuous wall is provided withan opening for the recuperation into said chamber of crop material whichhas been entrained by said apron assembly when the latter left saidbaling chamber and entered its outer run.

This recuperation opening preferably extends over the full width of thebaling chamber and may have a circumferential length which issubstantially equal to the distance between two consequent slats of theapron assembly. The opening according to the invention mayadvantageously be used in fixed chamber baler wherein the inner andouter runs of the apron assembly are guided along the inside and theoutside of the cylindrical wall.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in greater detail, with reference tothe accompanying drawings in which:

FIG. 1 is a cutaway side elevational view of a round baler, comprising amain frame, a pick-up assembly, a baling chamber with an apron conveyorand a wrapping apparatus;

FIGS. 2 and 3 are enlarged side elevational views of the area betweenthe pick-up assembly and the main frame of the baler of FIG. 1, showingthe pick-up assembly in two distinct working positions; and

FIGS. 4, 5 and 6 are side elevations views of the wrapping apparatus ofthe baler of FIG. 1 in selected conditions during operation.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings for a more detailed description of theinventions, FIG. 1 shows a round baler 10, including a main frame 11, afixed bale forming chamber 12 mounted onto this frame 11 for forming acylindrical package of crop material 13 therein, a pick-up assembly 14for picking up crop material, such as hay or straw, from the field anddelivering it to a rotatable conveyor 15 which feeds it into the baleforming chamber 12 while the baler 10 is moved across the field, and awrapping apparatus 16 for wrapping material such as plastic sheet or net17 around a completed cylindrical package 13 within the bale formingchamber 12.

The main frame 11 includes a main support beam 20 on which a pair ofwheels 21 (only one shown) is rotatably affixed. The frame 11 furtherincludes a pair of side walls 22 (only one shown) between which the baleforming chamber 12 extends.

The baler 10 also includes a tongue 23 extending from the forwardportion of the main frame 11 for conventional connection to a tractor.Pivotally connected to the side walls of the main frame 11 by a pair ofstub shafts 24 is a tailgate 25, which may be closed during baleformation, as shown in FIG. 1, or pivoted open about stub shafts 24 todischarge a completed bale. The tailgate 25 includes tailgate walls 26coextensive with the side walls 22.

The bale forming chamber 12 is defined primarily by an apron assembly 28comprising a pair of support chains 29 mounted to travel along acontinuous path, the inner run of which is defined on side walls 22 andtailgate walls 26 by front and rear sections 31, 32 of a continuouschain guide track that separates during bale discharge. The apronassembly 28 further comprises a plurality of parallel tubularcrop-engaging slats 33 extending between the chains 29 to provide acage-like periphery of the cylindrically shaped chamber 12. Radiallyoutwardly of the inner run of apron assembly 28 are front and rearsections 34, 35 of a continuous cylindrical bale chamber wall. Thesewall sections 34, 35, also separable during bale discharge, are mountedbetween the side walls 22 and the tailgate walls 26, respectively, formaintaining integrity between the outer and inner runs of the apronassembly 28 and for preventing losses of brittle and short stalks ofcrop material, which might otherwise fall from between the slats 33 ontothe field.

Operatively engaged with the chains 29 are drive sprockets 36 mountedbetween the side walls 22, idler sprockets 37 also mounted between theside walls 22 on the stub shafts 24, and idler sprockets 38 mountedbetween tailgate walls 26. A conventional chain drive system for thedrive sprockets 36 is provided via appropriate coupling to a gearbox 40in a conventional matter, depicted in phantom outline outwardly of sidewall 22.

The bale forming chamber 12 is further defined by the outer conveyingsurfaces of a floor roll 42 and a stripper roll 43, both of which aredriven in a clock-wise direction as seen in FIG. 1, by conventionaldrive means appropriately coupled to gearbox 40. These rolls 42, 43 areprovided with ribs 44, 45 to enhance their ability to convey crops inthe chamber 12 as a bale is being formed. Other forms of aggressivestructure may be used to accommodate various types of crops andconditions.

In the top portion of the front wall section 34, there is provided arectangular opening 47 extending over almost the full width of the baleforming chamber 12 and having a length in the circumferential directionwhich is substantially equal to the distance between to consequentconveyor slats 33.

During operation crop material is picked up from the field by thepick-up assembly 14 and delivered to the rotary conveyor 15 which inturn delivers the material to the bale chamber inlet 48, which isdefined between the floor roll 42 and the stripper roll 43. Within thebale forming chamber 12 the incoming material is engaged and rotated bythe slats 33 of the apron assembly 28. A portion of the crop stalksextends in between the slats 33 and may get caught between these slats33 and the bale chamber wall 34, 35. The slats 33 convey these stalksalong the inside of the wall and may eventually pull them out of thebale forming chamber 12, when the slats leave this chamber at the lowerend of the front wall section 34. The ribs 45 of the stripper roll 43 donot penetrate between the slats 33 and hence cannot engage the cropmaterial which is trapped between the slats 33 and the front wallsection 34.

However a substantial portion of the crop material which was trappedbetween the apron assembly 28 and the rear wall section 35 will neverreach the front portion of the bale forming chamber 12: when the slats33 pass along the rectangular opening 47, the trapped material is nolonger pressed against an inner wall and is released such that it canfall back into the bale forming chamber 12, where it can be incorporatedinto the cylindrical package 13. This recuperation is particularlyeffective as long the bale forming chamber 12 is not completely filledand the top portion thereof is containing no or only fluffy cropmaterial.

The trapped crop stalks which nevertheless reaches the exit of the apronassembly 28 above the stripper roll 43, are conveyed by the slats 33 outof the bale forming chamber 12 and along the outside of the front wallsection 34. When this material reaches the rectangular opening 47 it isreleased and falls back into the chamber 12, where it is incorporatedinto the cylindrical package 13. In prior art balers having a continuouschamber wall without recuperation opening, the trapped material wouldhave been conveyed over the top of the front and rear wall sections 34,35 and deposited rearwardly of the baler 10, such that it would be lostfor further bale formation.

While the preferred structure in which the principles of the presentinvention have been incorporated, is shown and described above, it is tobe understood that the invention is not to be limited to the particulardetails, as shown and described above, but that, in fact, widelydifferent means may be employed in the practice of the broader aspectsof the invention.

For example, it is conceivable to provide a recuperation opening inanother part of the front or rear wall section 34, 35 of the baleforming chamber 12. The single opening 47 may equally be replaced with aplurality of transversely arranged openings in the upper portion of oneof the wall sections 34, 35.

It will be appreciated that, according to the invention, means areprovided for, on the one hand, reducing the chance that crop materialremains trapped between the slats of an apron conveyor and a continuousinner wall of a bale chamber, and on the other hand, assisting inrecovering material which has been drawn out of the baling chamber bythese slats.

As shown in FIGS. 1, 2 and 3, the pick-up assembly 14 comprises apick-up frame 50 which is mounted for pivotment about a transverse pivotaxis 51 to and between two side wall extensions 52 (only one shown)which are extending downwardly from both side walls 22. These extensions52 equally hold the shaft of the rotary conveyor 15 and constitute theside walls of a duct registering with the inlet 48 of the bale formingchamber 12.

The pick-up 14 assembly further comprises a set of side-by-side arrangedguide plates 54 which are affixed to the pick-up frame 50. In aconventional manner four sets of pick-up tines 55 are travelled throughthe spacings between the guide plates 54 along a path 56, illustrated inphantom in FIGS. 2 and 3. Ground-engaging guide members, such as guidewheels 58, are rotatably mounted to the sides of the pick-up frame 50for limiting the clearance between the lower side of the guide membersand the ground surface.

A bracket 59 is welded to the rear portion of the pick-up frame 50 forholding therein the front end of a tubular positioning bar 60. The rearportion of this bar 60 is held for sliding movement in an opening of atransverse beam 61 which is welded to one of the side wall extensions52. The front portion of the positioning bar 60 is provided with aplurality of mounting holes 62 for a clevis pin 63. A flotation spring65 is mounted between a pair of washers 64 over the positioning bar 60.The front washer 64 is rested against a collar 66 mounted over the bar60 and secured thereto by the pin 63, while the rear washer 64 is heldagainst an identical collar 66 which is slideably mounted on thepositioning bar 60. A cushioning spring 68 is mounted between two otherwashers 67 between the rear collar 66 and the transverse beam 61. Thespring constant of this cushioning spring 68 is much greater than thespring constant of the flotation spring 65, such that a load on thefront end of the latter will primarily cause the compression of thisspring 65, while the length of the cushioning spring will not varysubstantially.

FIG. 2 shows the pick-up assembly 14 in a floating condition, i.e. thefull weight of this assembly 14 is not supported by the guide wheels 58,but the larger portion thereof is supported by the springs 65, 68. Whenthe baler 10 is travelled over the field, the wheels 58 follow theground contour and move the pick-up frame 50 upwardly and downwardly toadjust the path 56 of the pick-up tines 55 to the actual ground level.The position bar 60 slides back and forth through the opening in thebeam 51, while the flotation spring 65 extends and contracts between thefront collar 66, secured by the clevis pin 63, and the substantiallystationary intermediate collar 66.

The front collar 66 may be slid over the bar 60 and secured thereto bymounting the clevis pin 63 in another of the holes 62 for adapting thepick-up position to the hitch height of distinct tractors or for varyingthe compression of the flotation spring 65 and hence the portion of theweight of the pick-up assembly 14 which is compensated by this spring65.

The pick-up frame 50 can be pivoted upwardly and downwardly by means ofa single-acting hydraulic actuator 72, whereof the cylinder is pivotablyconnected to a support 73 which is welded above the beam 61 to side wallextension 52. The piston end carries a slotted extension 75 throughwhich extends a pin 76 which is affixed to a support 77 welded to theback of the pick-up frame 50. During baling operations the actuator 72is retracted or extended to make the centre of the pin 76 coincide withthe middle of the slot in the extension 75. When the pick-up assembly 14is oscillated while travelling over the field, the flotation spring 65may expand and retract accordingly. This movement is not hampered by thefixed position of the hydraulic actuator 72 as the pin 76 is permittedto travel back and forth within the limits of the slot of the actuatorextension 75. In case the field conditions change and the pin 76continuously engages the one or other slot end, such that free movementof the pick-up frame 50 is limited, freedom of movement can be restoredby adjusting the extension of the hydraulic actuator 72.

When the operator wishes to adjust the portion of the pick-up weightwhich is transferred upon the guide wheels 58, he can use the hydraulicactuator 72 to raise the pick-up frame 50 and pull the positioning bar60 forwardly. The flotation spring 65 and the cushioning spring 68 arereleased and the load on the clevis pin 63 is relieved. Now the springs65, 68 and the intermediate collar 66 can freely be shifted rearwardlyfor securing the front collar 66 by the clevis pin 63 to any of themounting holes 62 of the positioning bar 60. Thereafter the hydraulicactuator is retracted to lower the pick-up frame 50 and to load againthe flotation and the cushioning springs 65, 68.

This flotation system allows a close positioning of the pick-up tines 55to the ground, which is very advantageous in crops having nosubstantially high stubble such as hay. However, when baling othercrops, such as straw, this close positioning is not required and thepick-up assembly 14 may be travelled at a higher level above the ground,while the guide wheels 58 no longer have to be in permanent engagementwith the ground. This condition is illustrated in FIG. 3. Here theclevis pin 63 has been removed from the front portion of the positioningbar 60 and has been inserted through the intermediate collar 66 in amore rearward mounting hole 79 of this bar 60. The flotation spring 65is no longer loaded and the weight of the pick-up assembly 14 is nowtransferred via the positioning bar 60 and the collar 66 upon thecushioning spring 68. Because of its high spring constant this spring 68is hardly compressed, such that the choice of the mounting hole 79 forthe clevis pin 63 substantially determines the height of the pick-upassembly 14. The use of this cushioning spring 68 is advantageous inthat it dampens the shocks from the positioning bar 60 on the beam 61and hence on the main frame 11. Such shocks occur when the baler 10 istravelled over rough ground which induces a rocking movement to thepick-up assembly 14.

To vary the pick-up between a flotation condition as shown in FIG. 2 anda fixed height condition as shown in FIG. 3, or vice versa, thehydraulic actuator 72 is extended such that the pressure on the springs65, 68 is released. The clevis pin 63 can be removed to shift thesesprings and their intermediate collar 66 along the bar 60. The pin 63can now be reinserted in one of the mounting holes 62, 79 as required,whereafter the hydraulic actuator 72 is retracted to load again thecushioning spring 68 or the springs 65, 68.

While the preferred structure in which the principles of the presentinvention have been incorporated is shown and described above, it is tobe understood that the invention is not to be limited to the particulardetails, as shown and described above, but that, in fact, widelydifferent means may be employed in the practice of the broader aspectsof the invention.

For example, it is conceivable to provide a pick-up positioning systemwherein the rear end of the positioning bar 60 is pivotably affixed to abeam of the main frame 20, while its front end is slidably received in amember of the pick-up frame 50. A flotation spring then may be mountedfor compression between the pick-up frame 50 and a pin which is mountedin a hole in the rear portion of the bar. It is also conceivable to usesprings which are not mounted over the positioning rod 60, but whichextend parallel thereto and are engaged by an abutment means mountedonto this rod. The cushioning spring 68 may also be replaced withanother buffer means, such as a rubber socket. The pick-up positioningmeans of the invention may also be used in other crop-collectingmachinery, such as rectangular balers or loader wagons.

The wrapping apparatus 16 for wrapping material around a completed balewill now be described in further detail with reference to FIG. 4, whichshows this apparatus 16 while dispensing net 17 to the cylindricalpackage 13 rotated in the bale forming chamber 12.

The wrapping apparatus 16 comprises a net supply assembly 83, adispensing mechanism 84 for receiving wrapping material from the supplyassembly 83 and dispensing it to the bale forming chamber 12 and asevering assembly 85 for severing the wrapping material after it hasbeen wound around the completed cylindrical package 13.

The net supply assembly 16 comprises a support shaft 87 which is mountedfor rotation in apertures in the front portion of the side walls 22. Asupply roll of wrapping material 88, such as net, is mounted onto thisshaft 87 and secured thereto by appropriate means such as a barbsprojecting from the shaft 87 or a pair of cones secured thereto andinserted into the core of the supply roll 88. The net 17 is guided alongan idler roll 89 to the dispensing mechanism 84.

This mechanism 84 comprises a pair of parallel frame members 92 fixedlysecured to a rotatably supported cross tube 93 which extends between theside walls 22, and an upper and a lower clamping member 94, 95, both ofwhich have tips for grasping the net 17 in a fashion which is clearlydescribed in U.S. Pat. No. 4,956,968. Two spreader rolls 96, 97,provided with appropriate surface elements, such as spirals, forspreading the side strips of the dispensed net 17, extend between theframe members 92. The net 17 issued from the supply roll 88 is guidedfrom the idler roll 89 along a path around the spreader rolls 96, 97 tothe clamping members 94, 95.

Mounted outboard of the side wall 22 is an electrical actuator assembly98 comprising means for reciprocally driving an element 99 which ispivotally attached to one end of a link member 100. The other end ofthis link member 100 is fixedly secured to an outboard end of the crosstube 93. Extension and retraction of the actuator element 99 pivot theframe members 92 rearwardly and forwardly to deliver the net 17 to a gapbetween the exit of the apron assembly 28 and the stripper roll 43.

The net severing assembly 85 comprises a shear bar 103 fixedly mountedbetween the side walls 22 and a transverse knife 104 affixed to amounting member 105 extending between a pair of parallel knife supportarms 106 which are rotatably mounted at fixed pivot points 107 on theinside of the side walls 22. A coupling link 110 is pivotally attachedat its upper end to one of the frame members 92. Its lower end isreceived in a sliding bushing 111 which is pivotally attached to one ofthe knife support arms 106. The lower portion of the coupling link 110is provided with a stop nut 112 for adjusting the position of the knife104 to the shear bar 103 when the frame members 92 are pivoted to theiruppermost position, slightly above the position shown in FIGS. 4 and 5.

The wrapping apparatus 16 further comprises a drag control mechanism 114for maintaining the net 17 stretched between the net supply assembly 83and the bale forming chamber 12. This control mechanism 114 comprises asteel friction disc 115 which is secured to the outer end of the shaft87 of the net supply assembly 83. The periphery of this disc 115 isengaged by a brake shoe 116 provided with a lining of friction materialand affixed to a drag lever 117 which is pivotally attached to the sidewall 22. The upper arm of the lever 117 is pushed forwardly by a member118 of a load arm 119. Both the lever 117 and the load arm 119 arepivoted about a stud 120 which is welded onto the side wall 22.

The periphery of the net supply roll 88 is engaged by a transversesensor member 121 at the end of an forwardly and upwardly extendingsensor arm 122. This arm 122 is attached to the inner end of a pivotshaft 123 extending through the side wall 22. A pull arm 124 is fixedlyattached to the outer end of the shaft 123. A tension spring 126 ismounted between the pull arm 124 and an extension 127 of the load arm119 for forcing the brake shoe 116 onto the friction disc 115.

A rod 129 is pivotally attached to the upper end of the pull arm 124.The upper end of this rod 129 is slidingly received in a hole of a pivot130 which is attached to the upper portion of the side wall 22. Acompression spring 131 is mounted over the rod 129 and compressedbetween the pivot 130 and a pair of locking nuts 132 which are screwedon the rod 129. The position of the nuts 132 on the nuts may be changedto vary the compression the spring 131 and hence the force on the upperend of the pull arm 124.

Affixed to the load arm 119 is a release rod 135 whereof the rear end ismounted in a sliding yoke 136 which is pivotably attached to a releasearm 137 affixed to the cross tube 93. Rotation of this tube incounter-clockwise direction as seen in FIG. 4 slides the yoke 136 overthe rod 135 until it engages a stop member 138 near the end of the rod135 and pulls this rod and the load arm 119 rearwardly. The member 118of this arm 119 is released from the drag lever 117, such that the forceof the tension spring 126 is cancelled, but the lever 117 remains biasedtowards the friction disc 115 by a bias spring 141.

The brake shoe 116 can be lifted to release the friction disc 115completely by pushing a lever 143 rearwardly such that a stud 144 weldedto this lever 143 pushes the drag lever 117 and the load arm rearwardlyand engages a notch in the lever 117. This release operation is requiredwhen the baler 10 runs out of wrapping material and the supply roll 88has to be replaced.

FIG. 4 illustrates the operation of the wrapping apparatus 16 when abouthalf of the wrapping material available on a roll has been dispensed.The net 17 is unwound from the supply roll 88 and is guided along theidler roll 89, the spreader rolls 96, 97 and the clamping members 94, 95to the bale forming chamber 12 where it has been grasped by the rotatingcylindrical package 13. During this stage the actuator 98 has not beenfully retracted such that the support arm 106 of the net severingassembly 85 has not reached its uppermost position and there remains agap between the shear bar 103 and the knife 104 for feeding the net 17between.

On the one hand it is required that the net surface is pulled withsufficient force against the spreader rolls 96, 97 for effectivespreading of the material unrolled from the supply roll 88, and on theother hand this force has to be limited to prevent shearing of thismaterial. As the resistance against unwinding grows as the supply rolldiameter diminishes and the roll 88 is rotated more rapidly, the dragforce exerted by the brake shoe 116 has to be adapted to accordingly.This effect is generated by the drag control mechanism 114.

The diameter of the supply roll 88 is sensed by the sensor arm 122,which is forced against the roll surface by the tension spring 126. Aportion of this spring force is compensated by the force of thecompression spring 131 which pushes the pull arm 124 forwardly, suchthat the sensor arm member 121 has no significant braking effect on theroll 88. The roll diameter defines the position of the pull arm 124 andhence the extension of the tension spring 126. The force from thisspring is transferred upon load arm 119 and therefrom upon the draglever 117 which pushes the brake shoe 116 against the friction disc 115.

A full supply roll 88 will generate maximum spring extension and hencemaximum braking force for the rotation of the roll shaft 87. While theroll diameter decreases gradually during wrapping operations, the spring126 contracts accordingly and the braking force on the periphery of thefriction disc 115 decreases proportionally. Thus are provided means formaintaining the net 17 stretched with a substantially constant forceduring all wrapping operations.

When the roll 88 is almost completely unwound, as shown in FIG. 5, theload arm 124 has reached its rearmost position and is now extendingtowards the pivot 130 of the compression spring 131. Its spring forcesare assumed completely by the pivot 130 and the load arm shaft 123, suchthat they have no further effect on the roll-engaging member 121 of thesensor arm 122. The only force for holding this member 121 against theroll surface results from the tension spring 126 which has retracted inaccordance the roll diameter. Hence the effect of the decreasing springforces of the tension spring 126 on the roll surface is compensated byan equally decreasing spring forces of the compression spring 131.

FIG. 6 illustrates the wrapping apparatus 17 at the start of a wrappingoperation. Between wrapping operations the net dispensing mechanism 84is retracted in a position slightly above the position shown in FIGS. 4and 5. The net 17 has been severed by the severing assembly 85 and a nettail is extending between the clamping members 95, 96 and the knife 104while a compacted cylindrical package is being formed in the chamber 12.At the start of a new wrapping operation the actuator 98 is energized topivot the frame members 92 rearwardly and to lower the knife supportarms 106. The net tail is released from the knife 104 and conveyed bythe clamping members 94, 95 into the gap between the still rotatingapron assembly 28 and stripper roll 43. The ribs 45 on the stripper roll43 grasp the end of the net 17 and feed it to the nip between this roll43 and the surface of the cylindrical package of crop material. The net17 is further unwound from the supply roll 88 by the action of the stillrotating roll 43 and package.

During the rearward movement of the frame members 92 the sliding yoke136 on the release arm 137 engages the stop member 138 and pulls therelease rod 135 and the load arm 119 rearwardly, as described above. Thearm 119 disengages the drag lever 117, such that this lever is biasedtowards the friction disc 115 by the bias spring 141 only. The residualdrag force effected by the brake shoe 116 on the one hand is greatenough for providing some drag required for spreading the net 17 bymeans of the spreader rolls 96, 97 and on the other hand is small enoughto prevent extraction of the net tail from between the clamping members95, 96 during the rearward movement of the net dispensing mechanism 84.Omission of the bias spring 141 would allow a substantial transversecontraction of the net, such that the first winding around thecylindrical package 13 would not sufficiently cover the side portions ofits circumferential surface and additional windings of wrapping materialwould be required to obtain a solid and stable bale.

After feeding the net tail to the stripper roll 43, the net dispensingmechanism 84 returns to its position shown in FIGS. 4 and 5. The releasearm 137 is pivoted forwardly and the yoke 136 disengages the release rod135, such that the tension spring 126 can pull the load arm 119 againstthe drag lever 117 and provide full pressure upon the brake shoe 116.The drag forces on the net 17 increase accordingly such that thespreader rolls 96, 97 may spread the net effectively over the full widthof the bale forming chamber 12 during the remainder of the wrappingoperation.

While the preferred structure in which the principles of the presentinvention have been incorporated is shown and described above, it is tobe understood that the invention is not to be limited to the particulardetails, as shown and described above, but that, in fact, widelydifferent means may be employed in the practice of the broader aspectsof the invention. For example, it is conceivable to provide the supplyroll shaft 88 with a flat friction disk and brake shoes engaging theside surfaces of this disk. The drag control mechanism 114 of theinvention may also be combined with other types of net dispensingmechanisms, which e.g. may comprise a pair of feed rolls instead of apair of clamping members 94, 95 attached to a pair of movable members92.

It will be appreciated that thus is provided a wrapping apparatus with adrag control mechanism, which, on the one hand is not dependent on thetype of net or other wrapping material which is dispensed, and on theother is operable to apply a substantially constant drag force upon thesupplied wrapping material, irrespective of the quantity of materialavailable on the supply roll.

What is claimed is:
 1. A baler for forming crop material into cylindrical bales, said baler comprising a main frame and a baling chamber mounted on said main frame for forming cylindrical packages of crop material therein;said baling chamber being at least partially defined by a pair of side walls and an apron assembly having an inner run which is guided at the inside of a cylindrically shaped continuous wall, and an outer run which is guided at the outside of said continuous wall; and said continuous wall further comprising an opening for the recuperation into said chamber of crop material which has been entrained by said apron assembly when the latter left said baling chamber and entered its outer run wherein said opening extends over substantially the full width of the baling chamber wherein said apron assembly further comprises a pair of parallel support chains interconnected by equidistant slats; and said opening further comprises a circumferential length which is substantially equal to the distance between two consequent slats.
 2. The baler according claim 1, wherein the inner run of said apron assembly is guided along a fixed path adjacent the inside of said continuous wall.
 3. The baler according to claim 2, wherein the outer run of said apron assembly is guided along a fixed path adjacent the outside of said continuous wall.
 4. The baler according to claim 3, wherein said opening further comprises a wall section in the upper half of said baling chamber.
 5. The baler according to claim 4, wherein the baling chamber further comprises a front section which is affixed to said main frame and a rear section which is pivotally affixed to said front section, wherein said opening is provided in the front section where the apron assembly leaves said baling chamber. 